Pulverizing-mill.



G. L. PRATT.

PULVERIZING MILL. APPLICATION FILED AUG. 14, 1905.

PATENTED JULY 1'7, 1906.

2 SHEETSSHEET 1.

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PATENTED JULY 17; 1906.

G. LfPR-ATT. PULVERIZING MILL. APPLICATION FILED AUG. 14, 1905.

' 2 SHEETS-SHEET 2.

WITNESSES; I QM 1H: nonms rsrsns cu, WASHINGTON, a. c.

GEORGE LEWIS PRATT, OF ATLANTA, GEORGIA.

PULVERlZlNG-MILLi Specification of Letters Patent.

f Patented July 17, 1906.

Application filed August 14,1905. Serial No. 274,210.

To all whom, it may concern.-

Be it known that I, GEORGE LEWIS PRATT, a citizen of the United States,residing at Atlanta, in the county of Fulton and State of Georgia, haveinvented certain new and useful Improvements in Pulverizing-Mills; and Ido hereby declare the following to' be a full, clear, and exactdescription of the invention,

such as will enable others skilled in the art to which it app ertains tomake and use the same.

Much difficulty has been experienced in the past in securing from acentrifugal pulverizing-mill a product of sufficient fineness withoutthe use of separating-screens surrounding the pulverizing-chamber ofsuch fine mesh, and consequentlyso fragile, as to result in seriousdamage and wear and tear from the flying lumps or particles of thematerial deliv- %red to the interior of the pulverizing-cham- Among themore important objects, therefore, of my invention are, first, thepeculiar arrangement of a fine or final separating-screen relative to aninner heavier or coarser protecting-screen and the inclination of bothfine and coarse screens from the vertical line, whereby in operation thematerial passing the inner protecting-screen must necessarily fall uponthe outer or finishing screen, thereby giving a gravity separation whichmust necessarily result in the passage of all or at least the major partof the sufficiently fine material through the outer or finishing screenwithout serious wear and tear which necessarily occur if the inner orprotecting screen were not used; second, the peculiar formation orarrangement of a pulverizing-ring with relation to a pulverizing-rollerand with reference to the screens surrounding the pulverizing-chamber,whereby the splash resulting from the contact of the pulverizingrollerwith the material lying along the inner surface of the pulverizing-ringwill be practically parallel to the screens, thereby assisting toproduce a gravity separation which could not otherwise be obtained;third, the peculiar arrangement of the revolving table carrying theroll-shafts and forming the upper housing of the pulverizing-chamber andthe provision of strengthening-ribs placed underneath which table forsubserving the dual function of supports and of creating a blastwheeleffect, forcing a current of air against the screen which assists in theseparation and the cleaning of the screens, openings at or near thecenter of the revolving table allowing the introduction of the materialto be pulverized, said openings also permitting the ingress of airoccasioned by the said blast effect; fourth, the provision of anadditional housing above the top of the revolving table with openings ator near its center, so that any leakage or escape of dust from thepulverizing-chamber will be drawn back through the openings in the topof the revolving table.

With these objects in view and others the invention consists in thenovel construction, combination, and arrangement of parts, as will behereinafter fully described in the specification, illustrated in thedrawings, and summed up in the claims.

In the accompanying drawings, Figure 1 is a vertical section through myimproved pulverizing-machine. Fig. 2 is a horizontal section on line 11, and Fig. 3 is a horizontal section on line 2 2.

Referring to the drawings, the bed-plate or base A of the machine may bemade of any desired shape, preferably circular, and is formed with acurved conical annular flange c connected with an outer curved annularvflange a by radial ribs 0/, which flange a with the bottom aioonstitutes the pulverizing pan or receptacle for the incoming material.On the inner face of the pan a may be secured a conical pulverizing-ringB. Secured around an annular notch (1 in flange a is an annular drum orcasing a. Legs or standards C are secured to base A and extend upwardfor a distance and then converge and are bolted to a head D. Bolted tothe standards C is a spider E, which carries at its center the mainbearing F, which bearing carries the main vertical shaft G. Preferablybolted between the ribs or spokes of spider E are segmental covers ewhich are provided with annular downward-projecting curved flanges eprovided with annular notches to carry the annular casing a, an outerscreen a and an inner screen a. The lower edge of the outer screen a isdesirably carried by a conical flange a preferably forming part of thepulverizing member B, but in the drawings shown as separate and clampedthereto. The lower edge of the inside screen a is desirably carried bylugs or straps a, fixed at intervals to the flange at. These lugs aresufficiently separated from each other around the flange a to holdsecurely in position the bottom of the inner coarse screen a and at thesame time not to prevent the passage of material I which has passedthrough screen a and has IIO been rejected by screen a back into thepulverizing-pan-that is, not to prevent it from falling out at thebottom between the two screens of and a over the edge of the pulverizingmember B into the pan.

The main shaft G may be supported at its head 9 by various bearing-disksg g and g on the flanged bearing-lining g and is driven by gears H and Hand pulley H At the lower end of shaft G is carried the revolving tableJ, which is provided on its under side with ribs J for the support ofthe trunnion-blocks K. The table is finished at its outside edge so thatit will rotate very nearly adjacent to the segments a, as shown at jNear the center of revolving table J and immediately outside the hub areprovided openings 3' and the segments e not reaching entirely to thecenter of the spider E. Openings 6 are formed through any or all ofwhich and through the openings feed may be delivered to the machine andalso through which comes in air drawn in by the fan action of the ribs Junder table J. Car ried by ribs J and revolubly secured therebetween aretrunnion-heads K, into which are secured shafts K, carrying revolublerollers K The material to be pulverizedis fed into the machine throughany suitable hopper, (not shown,) falls downward into thepulverizing-chamber, is caught by the rollers K or the plows h andbrought out into contact with the pulverizing-ring B, where it iscrushed or pulverized by the rolling action of the rollers K on ring B.Any material more or less finely pulverized is splashed up onto thesurface of screen a, as is also other material thrown thereon by theaction of all the inner revolving parts. Any of such material, whethersplashed from the ring or thrown by the revolving parts, which is ofsufficient fineness passes through the coarse screen a and falls uponouter screen a where a further separation takes place of any degree offineness desired, determined only by the fineness of mesh of screen a".Any material rejected by screen a immediately falls back to be againcaught between the surface of the rollers K and the inner surface ofring B for further pulverization. Similarly material which has passedthrough screen a, but has been rejected by screen a falls between thetwo screens and in over the edge of the pulverizing-ring B to besimilarly further pulverized. Material of sufficient fineness havingpassed through both screens a and a is prevented from escaping by thecylindrical casing a and falls therefrom down through the spaces a,formed by the ribs a into a suitable hopper or conveyer underneath themachine. Similarly air drawn into the machine by the fan action of therevolving parts passes through the screens and down through the samechannels a, from whence it can be delivered in any direction desired.

It will be noticed that a small crack (shown at 9' must necessarilyexist between revolving table J and the downward-projecting flanges e ofthe segments 6 Also there must be some crack around the trunnion-heads Kwhere they fit into and are attached between the ribs J of revolvingtable J. (See Figs. 1 and 2.) If, therefore, no additional housing suchas is formed by these segments 6 were provided above the top of therevolving table, escape of dust through the cracks mentioned mustnecessarily be free to the outside air, and similarly would this be thecase if there were any openings in this housing other than those 0'',(shown at or about the center of the segmental covers 6 The housing eabove the top of the horizontal table J therefore subserves the veryimportant function of collecting and reintroducing at the center anyflying particles escaping from around the outside edge of the revolvingtable. The peculiar construction of the parts permits of absoluteclosing of the pulverizing-chamber except at or near the center, throughwhich there must necessarily be a suck of air rather than an outblow. Itwill further be noticed that a distinct advantage is gained by placingthe lower or driving pinion H below the main gear H, this advantagebeing twofoldfirst, the gear is between the bearings, and, second, thebelt leading away from pulley H the lower side of which is preferablythe pulling side, brings all of the wear on the horizontal bearing inthis shaft in one direction, and the inner bearing of this horizontalshaft acting as the fulcrum and the upper gear H as the work, similarlythe strain on this inner bearing must necessarily be in the samedirection as that on the outer bearing. Therefore the alinement isalwaysperfectly maintained.

Having thus fully described my invention, what I claim as new, anddesire to secure by Letters Patent, is

1. In a pulverizing-machine, a practicallyinclosed pulverizing-chamberformed at the bottom by a pulverizing-pan, at the sides by a surroundingdrum or casin and at the top by a housing open only at t e center; arevolving table supported beneath the housin and carryingroller-supporting shafts, said table being provided with openings at thecenter; and an outside and an inner screening-surface disposed about thepulverizingpan, and against which there is a fan action induced by theroller-shafts, when the machine is in operation.

2. In a pulverizing-machine,-a practicallyinclosed pulverizing-chamberformed at the bottom by a pulverizing-pan, at the sides by a surroundingdrum or casin and at the top by a housing open only at t e center; arevolving table supported beneath the housing and carryingroller-supporting shafts and having strengthening-ribs underneath, saidtable also being provided with openings at the center; and an outsideand an inner screening-surface disposed about the pulverizing-pan andagainst which there is a fan action induced by the ribs androller-shafts, when the machine is in operation.

3. In a pulverizing-maohine, a practicallyinclosed pulverizing-chamberformed at the bottom by a pulverizing-pan', at the sides by asurrounding drum or casing, and at the top by a housing open only at thecenter; a revolving table sup orted beneath the housing and carrying r0ler-supporting shafts and having strengthening-ribs underneath, saidtable also being provided with openings at the center; and an outsideand an inner screening-surface disposed about the pulverizing-pan and inclose proximity one to the other, and against whic there is a fan actioninduced by the ribs and roller-shafts, when the machine is in operation.

4. In a pulverizing-machine, a practicallyinclosed pulverizing-chamberformed at the bottom by a pulverizing-pan, at the sides by a surroundingdrum or casing, and at the top by a housing open only at the center; arevolving table supported beneath the housing and carryingroller-supporting shafts and having strengthening-ribs underneath, saidtable also being provided with openings at the center, and an outside,and an inside, heavier and coarser screening-surface disposed about thepulverizing-pan and in close proximity one to the other, and againstwhich there is a fan action induced by the ribs and roller-shafts, whenthe machine is in operation.

5. In a pulverizing-machine, a practicallyinclosed pulverizing-chamberformed at the bottom by a pulverizing-pan, at the sides by a surroundingdrum or casing, and at the top by a housing open only at the center;arevolving table sup orted beneath the housing and carrying roher-supporting shafts and having strengthening-ribs underneath, saidtable also being provided with openings at the center, and an outsideand an inner screening-surface slantingly disposed about thepulverizing-pan and in close proximity one to the other, whereby thereis a gravity separation of material thrown thereagainst, and againstwhich there is a fan action induced by the ribs and roller-shafts, whenthe machine is in operation.

6. In a pulverizing-machine, a practicall inclosed pulverizing-chamberformed at t e bottom by a pulverizing-pan, at the sides by a surroundingdrum or casin and at the top by a housing open only at t e center; arevolving table sup orted beneath the housing and carrying roler-supporting shafts and having strengthening-ribs underneath, saidtable also being provided with openings at the center, and an outsideand an inner screening-surface slantingly disposed about thepulverizing-pan and in close proximity one to the other; saidpulverizing-pan being formed with a grinding-surface having asubstantially parallel inclination to the slant or incline of thescreening-surfaces.

In testimony whereof I aflix my signature in the presence of twosubscribing witnesses.

GEO. LEWIS PRATT.

Witnesses:

WILL D. HANCOCK, T. B. FORD

